mirror of
https://github.com/zxing/zxing.git
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formatting only
git-svn-id: https://zxing.googlecode.com/svn/trunk@1839 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
smparkes@smparkes.net
parent
0d4ae9fef6
commit
395cdb0f24
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@ -1,4 +1,5 @@
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/*
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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* DecodedBitStreamParser.cpp
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* zxing
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*
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@ -37,317 +38,317 @@
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using namespace zxing;
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namespace zxing {
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namespace qrcode {
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namespace qrcode {
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using namespace std;
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using namespace std;
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const char DecodedBitStreamParser::ALPHANUMERIC_CHARS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B',
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'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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'Y', 'Z', ' ', '$', '%', '*', '+', '-', '.', '/', ':'
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};
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const char DecodedBitStreamParser::ALPHANUMERIC_CHARS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B',
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'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
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'Y', 'Z', ' ', '$', '%', '*', '+', '-', '.', '/', ':'
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};
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const char *DecodedBitStreamParser::ASCII = "ASCII";
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const char *DecodedBitStreamParser::ISO88591 = "ISO-8859-1";
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const char *DecodedBitStreamParser::UTF8 = "UTF-8";
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const char *DecodedBitStreamParser::SHIFT_JIS = "SHIFT_JIS";
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const char *DecodedBitStreamParser::EUC_JP = "EUC-JP";
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const char *DecodedBitStreamParser::ASCII = "ASCII";
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const char *DecodedBitStreamParser::ISO88591 = "ISO-8859-1";
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const char *DecodedBitStreamParser::UTF8 = "UTF-8";
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const char *DecodedBitStreamParser::SHIFT_JIS = "SHIFT_JIS";
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const char *DecodedBitStreamParser::EUC_JP = "EUC-JP";
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void DecodedBitStreamParser::append(std::string &result, const unsigned char *bufIn, size_t nIn, const char *src) {
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void DecodedBitStreamParser::append(std::string &result, const unsigned char *bufIn, size_t nIn, const char *src) {
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#ifndef NO_ICONV
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if (nIn == 0) {
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return;
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}
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iconv_t cd = iconv_open(UTF8, src);
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const int maxOut = 4 * nIn + 1;
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unsigned char* bufOut = new unsigned char[maxOut];
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ICONV_CONST char *fromPtr = (ICONV_CONST char *)bufIn;
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size_t nFrom = nIn;
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char *toPtr = (char *)bufOut;
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size_t nTo = maxOut;
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while (nFrom > 0) {
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size_t oneway = iconv(cd, &fromPtr, &nFrom, &toPtr, &nTo);
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if (oneway == (size_t)(-1)) {
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iconv_close(cd);
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delete[] bufOut;
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throw ReaderException("error converting characters");
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}
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}
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iconv_close(cd);
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int nResult = maxOut - nTo;
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bufOut[nResult] = '\0';
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result.append((const char *)bufOut);
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delete[] bufOut;
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#else
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result.append((const char *)bufIn, nIn);
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#endif
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}
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void DecodedBitStreamParser::decodeKanjiSegment(Ref<BitSource> bits, std::string &result, int count) {
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// Each character will require 2 bytes. Read the characters as 2-byte pairs
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// and decode as Shift_JIS afterwards
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size_t nBytes = 2 * count;
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unsigned char* buffer = new unsigned char[nBytes];
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int offset = 0;
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while (count > 0) {
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// Each 13 bits encodes a 2-byte character
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int twoBytes = bits->readBits(13);
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int assembledTwoBytes = ((twoBytes / 0x0C0) << 8) | (twoBytes % 0x0C0);
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if (assembledTwoBytes < 0x01F00) {
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// In the 0x8140 to 0x9FFC range
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assembledTwoBytes += 0x08140;
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} else {
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// In the 0xE040 to 0xEBBF range
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assembledTwoBytes += 0x0C140;
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}
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buffer[offset] = (unsigned char)(assembledTwoBytes >> 8);
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buffer[offset + 1] = (unsigned char)assembledTwoBytes;
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offset += 2;
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count--;
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}
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append(result, buffer, nBytes, SHIFT_JIS);
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delete[] buffer;
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}
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void DecodedBitStreamParser::decodeByteSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* readBytes = new unsigned char[nBytes];
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if (count << 3 > bits->available()) {
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ostringstream s;
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s << "Count too large: " << count;
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delete[] readBytes;
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throw ReaderException(s.str().c_str());
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}
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for (int i = 0; i < count; i++) {
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readBytes[i] = (unsigned char)bits->readBits(8);
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}
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// The spec isn't clear on this mode; see
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// section 6.4.5: t does not say which encoding to assuming
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// upon decoding. I have seen ISO-8859-1 used as well as
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// Shift_JIS -- without anything like an ECI designator to
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// give a hint.
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const char *encoding = guessEncoding(readBytes, nBytes);
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append(result, readBytes, nBytes, encoding);
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delete[] readBytes;
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}
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void DecodedBitStreamParser::decodeNumericSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* bytes = new unsigned char[nBytes];
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int i = 0;
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// Read three digits at a time
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while (count >= 3) {
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// Each 10 bits encodes three digits
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int threeDigitsBits = bits->readBits(10);
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if (threeDigitsBits >= 1000) {
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ostringstream s;
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s << "Illegal value for 3-digit unit: " << threeDigitsBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[threeDigitsBits / 100];
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bytes[i++] = ALPHANUMERIC_CHARS[(threeDigitsBits / 10) % 10];
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bytes[i++] = ALPHANUMERIC_CHARS[threeDigitsBits % 10];
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count -= 3;
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}
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if (count == 2) {
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// Two digits left over to read, encoded in 7 bits
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int twoDigitsBits = bits->readBits(7);
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if (twoDigitsBits >= 100) {
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ostringstream s;
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s << "Illegal value for 2-digit unit: " << twoDigitsBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[twoDigitsBits / 10];
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bytes[i++] = ALPHANUMERIC_CHARS[twoDigitsBits % 10];
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} else if (count == 1) {
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// One digit left over to read
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int digitBits = bits->readBits(4);
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if (digitBits >= 10) {
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ostringstream s;
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s << "Illegal value for digit unit: " << digitBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[digitBits];
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}
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append(result, bytes, nBytes, ASCII);
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delete[] bytes;
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}
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void DecodedBitStreamParser::decodeAlphanumericSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* bytes = new unsigned char[nBytes];
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int i = 0;
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// Read two characters at a time
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while (count > 1) {
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int nextTwoCharsBits = bits->readBits(11);
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bytes[i++] = ALPHANUMERIC_CHARS[nextTwoCharsBits / 45];
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bytes[i++] = ALPHANUMERIC_CHARS[nextTwoCharsBits % 45];
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count -= 2;
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}
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if (count == 1) {
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bytes[i++] = ALPHANUMERIC_CHARS[bits->readBits(6)];
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}
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append(result, bytes, nBytes, ASCII);
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delete[] bytes;
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}
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const char *
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DecodedBitStreamParser::guessEncoding(unsigned char *bytes, int length) {
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const bool ASSUME_SHIFT_JIS = false;
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char const* const PLATFORM_DEFAULT_ENCODING="UTF-8";
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// Does it start with the UTF-8 byte order mark? then guess it's UTF-8
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if (length > 3 && bytes[0] == (unsigned char)0xEF && bytes[1] == (unsigned char)0xBB && bytes[2]
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== (unsigned char)0xBF) {
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return UTF8;
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}
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// For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS,
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// which should be by far the most common encodings. ISO-8859-1
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// should not have bytes in the 0x80 - 0x9F range, while Shift_JIS
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// uses this as a first byte of a two-byte character. If we see this
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// followed by a valid second byte in Shift_JIS, assume it is Shift_JIS.
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// If we see something else in that second byte, we'll make the risky guess
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// that it's UTF-8.
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bool canBeISO88591 = true;
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bool canBeShiftJIS = true;
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bool canBeUTF8 = true;
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int utf8BytesLeft = 0;
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int maybeDoubleByteCount = 0;
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int maybeSingleByteKatakanaCount = 0;
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bool sawLatin1Supplement = false;
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bool sawUTF8Start = false;
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bool lastWasPossibleDoubleByteStart = false;
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for (int i = 0;
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i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8);
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i++) {
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int value = bytes[i] & 0xFF;
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// UTF-8 stuff
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if (value >= 0x80 && value <= 0xBF) {
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if (utf8BytesLeft > 0) {
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utf8BytesLeft--;
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if (nIn == 0) {
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return;
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}
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iconv_t cd = iconv_open(UTF8, src);
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const int maxOut = 4 * nIn + 1;
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unsigned char* bufOut = new unsigned char[maxOut];
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ICONV_CONST char *fromPtr = (ICONV_CONST char *)bufIn;
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size_t nFrom = nIn;
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char *toPtr = (char *)bufOut;
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size_t nTo = maxOut;
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while (nFrom > 0) {
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size_t oneway = iconv(cd, &fromPtr, &nFrom, &toPtr, &nTo);
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if (oneway == (size_t)(-1)) {
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iconv_close(cd);
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delete[] bufOut;
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throw ReaderException("error converting characters");
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}
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}
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iconv_close(cd);
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int nResult = maxOut - nTo;
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bufOut[nResult] = '\0';
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result.append((const char *)bufOut);
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delete[] bufOut;
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#else
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result.append((const char *)bufIn, nIn);
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#endif
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}
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void DecodedBitStreamParser::decodeKanjiSegment(Ref<BitSource> bits, std::string &result, int count) {
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// Each character will require 2 bytes. Read the characters as 2-byte pairs
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// and decode as Shift_JIS afterwards
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size_t nBytes = 2 * count;
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unsigned char* buffer = new unsigned char[nBytes];
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int offset = 0;
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while (count > 0) {
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// Each 13 bits encodes a 2-byte character
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int twoBytes = bits->readBits(13);
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int assembledTwoBytes = ((twoBytes / 0x0C0) << 8) | (twoBytes % 0x0C0);
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if (assembledTwoBytes < 0x01F00) {
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// In the 0x8140 to 0x9FFC range
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assembledTwoBytes += 0x08140;
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} else {
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// In the 0xE040 to 0xEBBF range
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assembledTwoBytes += 0x0C140;
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}
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buffer[offset] = (unsigned char)(assembledTwoBytes >> 8);
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buffer[offset + 1] = (unsigned char)assembledTwoBytes;
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offset += 2;
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count--;
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}
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append(result, buffer, nBytes, SHIFT_JIS);
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delete[] buffer;
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}
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void DecodedBitStreamParser::decodeByteSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* readBytes = new unsigned char[nBytes];
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if (count << 3 > bits->available()) {
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ostringstream s;
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s << "Count too large: " << count;
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delete[] readBytes;
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throw ReaderException(s.str().c_str());
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}
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for (int i = 0; i < count; i++) {
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readBytes[i] = (unsigned char)bits->readBits(8);
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}
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// The spec isn't clear on this mode; see
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// section 6.4.5: t does not say which encoding to assuming
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// upon decoding. I have seen ISO-8859-1 used as well as
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// Shift_JIS -- without anything like an ECI designator to
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// give a hint.
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const char *encoding = guessEncoding(readBytes, nBytes);
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append(result, readBytes, nBytes, encoding);
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delete[] readBytes;
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}
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void DecodedBitStreamParser::decodeNumericSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* bytes = new unsigned char[nBytes];
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int i = 0;
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// Read three digits at a time
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while (count >= 3) {
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// Each 10 bits encodes three digits
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int threeDigitsBits = bits->readBits(10);
|
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if (threeDigitsBits >= 1000) {
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ostringstream s;
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s << "Illegal value for 3-digit unit: " << threeDigitsBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[threeDigitsBits / 100];
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bytes[i++] = ALPHANUMERIC_CHARS[(threeDigitsBits / 10) % 10];
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bytes[i++] = ALPHANUMERIC_CHARS[threeDigitsBits % 10];
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count -= 3;
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}
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if (count == 2) {
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// Two digits left over to read, encoded in 7 bits
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int twoDigitsBits = bits->readBits(7);
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if (twoDigitsBits >= 100) {
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ostringstream s;
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s << "Illegal value for 2-digit unit: " << twoDigitsBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[twoDigitsBits / 10];
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bytes[i++] = ALPHANUMERIC_CHARS[twoDigitsBits % 10];
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} else if (count == 1) {
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// One digit left over to read
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int digitBits = bits->readBits(4);
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if (digitBits >= 10) {
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ostringstream s;
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s << "Illegal value for digit unit: " << digitBits;
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delete[] bytes;
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throw ReaderException(s.str().c_str());
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}
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bytes[i++] = ALPHANUMERIC_CHARS[digitBits];
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}
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append(result, bytes, nBytes, ASCII);
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delete[] bytes;
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}
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void DecodedBitStreamParser::decodeAlphanumericSegment(Ref<BitSource> bits, std::string &result, int count) {
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int nBytes = count;
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unsigned char* bytes = new unsigned char[nBytes];
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int i = 0;
|
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// Read two characters at a time
|
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while (count > 1) {
|
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int nextTwoCharsBits = bits->readBits(11);
|
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bytes[i++] = ALPHANUMERIC_CHARS[nextTwoCharsBits / 45];
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bytes[i++] = ALPHANUMERIC_CHARS[nextTwoCharsBits % 45];
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count -= 2;
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}
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if (count == 1) {
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bytes[i++] = ALPHANUMERIC_CHARS[bits->readBits(6)];
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}
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append(result, bytes, nBytes, ASCII);
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delete[] bytes;
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}
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const char *
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DecodedBitStreamParser::guessEncoding(unsigned char *bytes, int length) {
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const bool ASSUME_SHIFT_JIS = false;
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char const* const PLATFORM_DEFAULT_ENCODING="UTF-8";
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|
||||
// Does it start with the UTF-8 byte order mark? then guess it's UTF-8
|
||||
if (length > 3 && bytes[0] == (unsigned char)0xEF && bytes[1] == (unsigned char)0xBB && bytes[2]
|
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== (unsigned char)0xBF) {
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return UTF8;
|
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}
|
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// For now, merely tries to distinguish ISO-8859-1, UTF-8 and Shift_JIS,
|
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// which should be by far the most common encodings. ISO-8859-1
|
||||
// should not have bytes in the 0x80 - 0x9F range, while Shift_JIS
|
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// uses this as a first byte of a two-byte character. If we see this
|
||||
// followed by a valid second byte in Shift_JIS, assume it is Shift_JIS.
|
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// If we see something else in that second byte, we'll make the risky guess
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// that it's UTF-8.
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bool canBeISO88591 = true;
|
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bool canBeShiftJIS = true;
|
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bool canBeUTF8 = true;
|
||||
int utf8BytesLeft = 0;
|
||||
int maybeDoubleByteCount = 0;
|
||||
int maybeSingleByteKatakanaCount = 0;
|
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bool sawLatin1Supplement = false;
|
||||
bool sawUTF8Start = false;
|
||||
bool lastWasPossibleDoubleByteStart = false;
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for (int i = 0;
|
||||
i < length && (canBeISO88591 || canBeShiftJIS || canBeUTF8);
|
||||
i++) {
|
||||
int value = bytes[i] & 0xFF;
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// UTF-8 stuff
|
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if (value >= 0x80 && value <= 0xBF) {
|
||||
if (utf8BytesLeft > 0) {
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||||
utf8BytesLeft--;
|
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}
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} else {
|
||||
if (utf8BytesLeft > 0) {
|
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canBeUTF8 = false;
|
||||
}
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||||
if (value >= 0xC0 && value <= 0xFD) {
|
||||
sawUTF8Start = true;
|
||||
int valueCopy = value;
|
||||
while ((valueCopy & 0x40) != 0) {
|
||||
utf8BytesLeft++;
|
||||
valueCopy <<= 1;
|
||||
}
|
||||
}
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||||
}
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// Shift_JIS stuff
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||||
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||||
if (value >= 0xA1 && value <= 0xDF) {
|
||||
// count the number of characters that might be a Shift_JIS single-byte Katakana character
|
||||
if (!lastWasPossibleDoubleByteStart) {
|
||||
maybeSingleByteKatakanaCount++;
|
||||
}
|
||||
}
|
||||
if (!lastWasPossibleDoubleByteStart &&
|
||||
((value >= 0xF0 && value <= 0xFF) || value == 0x80 || value == 0xA0)) {
|
||||
canBeShiftJIS = false;
|
||||
}
|
||||
if (((value >= 0x81 && value <= 0x9F) || (value >= 0xE0 && value <= 0xEF))) {
|
||||
// These start double-byte characters in Shift_JIS. Let's see if it's followed by a valid
|
||||
// second byte.
|
||||
if (lastWasPossibleDoubleByteStart) {
|
||||
// If we just checked this and the last byte for being a valid double-byte
|
||||
// char, don't check starting on this byte. If this and the last byte
|
||||
// formed a valid pair, then this shouldn't be checked to see if it starts
|
||||
// a double byte pair of course.
|
||||
lastWasPossibleDoubleByteStart = false;
|
||||
} else {
|
||||
// ... otherwise do check to see if this plus the next byte form a valid
|
||||
// double byte pair encoding a character.
|
||||
lastWasPossibleDoubleByteStart = true;
|
||||
if (i >= length - 1) {
|
||||
canBeShiftJIS = false;
|
||||
} else {
|
||||
int nextValue = bytes[i + 1] & 0xFF;
|
||||
if (nextValue < 0x40 || nextValue > 0xFC) {
|
||||
canBeShiftJIS = false;
|
||||
} else {
|
||||
maybeDoubleByteCount++;
|
||||
}
|
||||
// There is some conflicting information out there about which bytes can follow which in
|
||||
// double-byte Shift_JIS characters. The rule above seems to be the one that matches practice.
|
||||
}
|
||||
}
|
||||
} else {
|
||||
lastWasPossibleDoubleByteStart = false;
|
||||
}
|
||||
}
|
||||
} else {
|
||||
if (utf8BytesLeft > 0) {
|
||||
canBeUTF8 = false;
|
||||
}
|
||||
if (value >= 0xC0 && value <= 0xFD) {
|
||||
sawUTF8Start = true;
|
||||
int valueCopy = value;
|
||||
while ((valueCopy & 0x40) != 0) {
|
||||
utf8BytesLeft++;
|
||||
valueCopy <<= 1;
|
||||
}
|
||||
|
||||
// Easy -- if assuming Shift_JIS and no evidence it can't be, done
|
||||
if (canBeShiftJIS && ASSUME_SHIFT_JIS) {
|
||||
return SHIFT_JIS;
|
||||
}
|
||||
if (canBeUTF8 && sawUTF8Start) {
|
||||
return UTF8;
|
||||
}
|
||||
// Distinguishing Shift_JIS and ISO-8859-1 can be a little tough. The crude heuristic is:
|
||||
// - If we saw
|
||||
// - at least 3 bytes that starts a double-byte value (bytes that are rare in ISO-8859-1), or
|
||||
// - over 5% of bytes could be single-byte Katakana (also rare in ISO-8859-1),
|
||||
// - and, saw no sequences that are invalid in Shift_JIS, then we conclude Shift_JIS
|
||||
if (canBeShiftJIS && (maybeDoubleByteCount >= 3 || 20 * maybeSingleByteKatakanaCount > length)) {
|
||||
return SHIFT_JIS;
|
||||
}
|
||||
// Otherwise, we default to ISO-8859-1 unless we know it can't be
|
||||
if (!sawLatin1Supplement && canBeISO88591) {
|
||||
return ISO88591;
|
||||
}
|
||||
// Otherwise, we take a wild guess with platform encoding
|
||||
return PLATFORM_DEFAULT_ENCODING;
|
||||
}
|
||||
|
||||
// Shift_JIS stuff
|
||||
|
||||
if (value >= 0xA1 && value <= 0xDF) {
|
||||
// count the number of characters that might be a Shift_JIS single-byte Katakana character
|
||||
if (!lastWasPossibleDoubleByteStart) {
|
||||
maybeSingleByteKatakanaCount++;
|
||||
}
|
||||
}
|
||||
if (!lastWasPossibleDoubleByteStart &&
|
||||
((value >= 0xF0 && value <= 0xFF) || value == 0x80 || value == 0xA0)) {
|
||||
canBeShiftJIS = false;
|
||||
}
|
||||
if (((value >= 0x81 && value <= 0x9F) || (value >= 0xE0 && value <= 0xEF))) {
|
||||
// These start double-byte characters in Shift_JIS. Let's see if it's followed by a valid
|
||||
// second byte.
|
||||
if (lastWasPossibleDoubleByteStart) {
|
||||
// If we just checked this and the last byte for being a valid double-byte
|
||||
// char, don't check starting on this byte. If this and the last byte
|
||||
// formed a valid pair, then this shouldn't be checked to see if it starts
|
||||
// a double byte pair of course.
|
||||
lastWasPossibleDoubleByteStart = false;
|
||||
} else {
|
||||
// ... otherwise do check to see if this plus the next byte form a valid
|
||||
// double byte pair encoding a character.
|
||||
lastWasPossibleDoubleByteStart = true;
|
||||
if (i >= length - 1) {
|
||||
canBeShiftJIS = false;
|
||||
string DecodedBitStreamParser::decode(ArrayRef<unsigned char> bytes, Version *version) {
|
||||
string result;
|
||||
Ref<BitSource> bits(new BitSource(bytes));
|
||||
Mode *mode = &Mode::TERMINATOR;
|
||||
do {
|
||||
// While still another segment to read...
|
||||
if (bits->available() < 4) {
|
||||
// OK, assume we're done. Really, a TERMINATOR mode should have been recorded here
|
||||
mode = &Mode::TERMINATOR;
|
||||
} else {
|
||||
int nextValue = bytes[i + 1] & 0xFF;
|
||||
if (nextValue < 0x40 || nextValue > 0xFC) {
|
||||
canBeShiftJIS = false;
|
||||
} else {
|
||||
maybeDoubleByteCount++;
|
||||
}
|
||||
// There is some conflicting information out there about which bytes can follow which in
|
||||
// double-byte Shift_JIS characters. The rule above seems to be the one that matches practice.
|
||||
mode = &Mode::forBits(bits->readBits(4)); // mode is encoded by 4 bits
|
||||
}
|
||||
}
|
||||
} else {
|
||||
lastWasPossibleDoubleByteStart = false;
|
||||
if (mode != &Mode::TERMINATOR) {
|
||||
// How many characters will follow, encoded in this mode?
|
||||
int count = bits->readBits(mode->getCharacterCountBits(version));
|
||||
if (mode == &Mode::NUMERIC) {
|
||||
decodeNumericSegment(bits, result, count);
|
||||
} else if (mode == &Mode::ALPHANUMERIC) {
|
||||
decodeAlphanumericSegment(bits, result, count);
|
||||
} else if (mode == &Mode::BYTE) {
|
||||
decodeByteSegment(bits, result, count);
|
||||
} else if (mode == &Mode::KANJI) {
|
||||
decodeKanjiSegment(bits, result, count);
|
||||
} else {
|
||||
throw ReaderException("Unsupported mode indicator");
|
||||
}
|
||||
}
|
||||
} while (mode != &Mode::TERMINATOR);
|
||||
return result;
|
||||
}
|
||||
}
|
||||
if (utf8BytesLeft > 0) {
|
||||
canBeUTF8 = false;
|
||||
}
|
||||
|
||||
// Easy -- if assuming Shift_JIS and no evidence it can't be, done
|
||||
if (canBeShiftJIS && ASSUME_SHIFT_JIS) {
|
||||
return SHIFT_JIS;
|
||||
}
|
||||
if (canBeUTF8 && sawUTF8Start) {
|
||||
return UTF8;
|
||||
}
|
||||
// Distinguishing Shift_JIS and ISO-8859-1 can be a little tough. The crude heuristic is:
|
||||
// - If we saw
|
||||
// - at least 3 bytes that starts a double-byte value (bytes that are rare in ISO-8859-1), or
|
||||
// - over 5% of bytes could be single-byte Katakana (also rare in ISO-8859-1),
|
||||
// - and, saw no sequences that are invalid in Shift_JIS, then we conclude Shift_JIS
|
||||
if (canBeShiftJIS && (maybeDoubleByteCount >= 3 || 20 * maybeSingleByteKatakanaCount > length)) {
|
||||
return SHIFT_JIS;
|
||||
}
|
||||
// Otherwise, we default to ISO-8859-1 unless we know it can't be
|
||||
if (!sawLatin1Supplement && canBeISO88591) {
|
||||
return ISO88591;
|
||||
}
|
||||
// Otherwise, we take a wild guess with platform encoding
|
||||
return PLATFORM_DEFAULT_ENCODING;
|
||||
}
|
||||
|
||||
string DecodedBitStreamParser::decode(ArrayRef<unsigned char> bytes, Version *version) {
|
||||
string result;
|
||||
Ref<BitSource> bits(new BitSource(bytes));
|
||||
Mode *mode = &Mode::TERMINATOR;
|
||||
do {
|
||||
// While still another segment to read...
|
||||
if (bits->available() < 4) {
|
||||
// OK, assume we're done. Really, a TERMINATOR mode should have been recorded here
|
||||
mode = &Mode::TERMINATOR;
|
||||
} else {
|
||||
mode = &Mode::forBits(bits->readBits(4)); // mode is encoded by 4 bits
|
||||
}
|
||||
if (mode != &Mode::TERMINATOR) {
|
||||
// How many characters will follow, encoded in this mode?
|
||||
int count = bits->readBits(mode->getCharacterCountBits(version));
|
||||
if (mode == &Mode::NUMERIC) {
|
||||
decodeNumericSegment(bits, result, count);
|
||||
} else if (mode == &Mode::ALPHANUMERIC) {
|
||||
decodeAlphanumericSegment(bits, result, count);
|
||||
} else if (mode == &Mode::BYTE) {
|
||||
decodeByteSegment(bits, result, count);
|
||||
} else if (mode == &Mode::KANJI) {
|
||||
decodeKanjiSegment(bits, result, count);
|
||||
} else {
|
||||
throw ReaderException("Unsupported mode indicator");
|
||||
}
|
||||
}
|
||||
} while (mode != &Mode::TERMINATOR);
|
||||
return result;
|
||||
}
|
||||
|
||||
}
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in a new issue